Rupert Murdoch's global empire spans publishing, broadcasting, film and the web, with annual revenues that last year totalled a record $33bn (£20bn). His News Corp business is home to the UK's largest newspaper group, News International, and it has a 39% stake in the country's biggest commercial broadcaster, BSkyB.

That Murdoch is not further up this list is a reflection of his preoccupation with his business interests in the United States, in particular his $5.6bn takeover of Wall Street Journal publisher Dow Jones.

Responsibility for his UK interests has been largely devolved to his son James, the chairman and chief executive of News Corp in Europe and Asia, and chairman of BSkyB (and three places above him in this year's MediaGuardian 100), and newly installed News International chief executive, Rebekah Wade. "It's the James and Rebekah show," said our panel.

Yet the News Corp chairman and chief executive remains a hugely influential figure. When Murdoch indicates a change in strategy, the rest of the media industry takes notice, not least when he raised the prospect that his newspapers would start to charge for online access. It began a debate that is likely to grip the sector for the next 12 months and beyond.

And it will be Murdoch who decides where the Sun casts its vote in the run-up to the general election. It may have turned its back on Gordon Brown's Labour, but when will it embrace David Cameron's Conservatives, if at all?

"He is completely preoccupied with the Wall Street Journal, but don't underestimate the influence of Murdoch in an election year," said our panel. "His influence remains enormous."

Murdoch was the old media baron who stole a march on his new media rivals with the purchase of MySpace for $580m in 2005. But the social networking site has long been eclipsed by its rivals such as Facebook and Murdoch has turned his attention to how his newspapers can generate more money on the web.

Murdoch warned that the current business model was "flawed" and said he expected to charge for access for News Corporation's newspaper websites within a year.

"We are now in the midst of an epochal debate over the value of content and it is clear to many newspapers that the current model is malfunctioning," said Murdoch. "That it is possible to charge for content on the web is obvious from the Wall Street Journal's experience," he said. But will users be prepared to pay outside of the specialist news arena?

The News Corp empire boasts the biggest-selling stable of newspapers in the English-speaking world as well as one of America's biggest television networks, Fox, and one of its biggest film studios, 20th Century Fox, which distributed the multiple Oscar-winning Film4 hit, Slumdog Millionaire. It also owns publishing house HarperCollins, Star TV in Asia, Sky Italia in Italy and Foxtel in Australia.

News Corp's full-year operating profits were $5.4bn in 12 months to end of June last year, up 21% on the previous year, but it reported a 97% fall in profits at its newspaper division in the first quarter of 2009 as the recession began to bite, down to $7m from $216m a year ago. Advertising revenue fell a fifth in the UK in the first three months of the year, with the Sunday Times "particularly hard hit", according to Murdoch.

Murdoch said the crisis hitting his media empire was the "worst downturn since News Corp was established 50 years ago". But he predicted in May that the downturn had bottomed out. "I am not an economist, and we all know that economists were created to make weather forecasts look good, but it is increasingly clear that the worst is over," he said.

It is unclear whether the revelations about phone-hacking at the News of the World will affect Murdoch's global empire.

Murdoch, who is based mostly in New York with his third wife, Wendi Deng, and their two young daughters, turned 78 this year but shows few signs of slowing down just yet.

His number two, Peter Chernin, quit News Corp this year, sparking speculation that James – long seen as the heir apparent to the family empire – would be moving to the US rather sooner than expected.

But Murdoch hired Chase Carey, his former close lieutenant and chief executive of DirecTV, to be his number two, taking on the role of deputy chairman, president and chief operating officer of News Corp. The family handover – if that is how the succession pans out – will have to wait a little longer yet.

Issuing a rallying cry to the industry at the end of last year, Murdoch dismissed suggestions that the internet would kill off newspapers. He said industry doomsayers were "misguided cynics". While print circulations would decline, he said there would be gains in areas such as websites and mobile phones.

"Unlike the doom and gloomers, I believe that newspapers will reach new heights in the 21st century. The form of delivery may change, but the potential audience for our content will multiply many times over. Our real business isn't printing on dead trees. It's giving our readers great journalism and great judgment."

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